Many types of manufacturing operations require the transmission of individual cylindrical components to an assembly station for automatic or manual incorporation of the component into a product or subassembly. In particular, the manufacture of electronic products frequently utilizes large numbers of axial lead electronic components, such as resistors, diodes and capacitors. These components are often obtained in bulk, and must be dispensed serially in a manner permitting their utilization in such operations as automatic or manual insertion into circuit boards.
Some manufacturing operations require testing of bulk components before their use in succeeding manufacturing operations. Also, non-bilateral symmetry devices such as semiconductor diodes require proper orientation before insertion into circuit assemblies, and means must be provided to provide 180 degree, end-for-end rotation of those devices which are improperly oriented.
The abovementioned requirements for rapidly feeding, testing and orienting axial lead components have understandably stimulated a great deal of inventive activity directed towards producing machines capable of rapid and efficient performance of the parts-handling tasks. That activity has resulted in the disclosure of a large variety of machinery of varying capabilities, as a study of the prior art will reveal.
Accordingly, an exhaustive summary of the prior art would be too lengthy and not suit the purposes of this disclosure. Instead, certain general features and drawbacks of previously disclosed machinery will be mentioned, to facilitate an appreciation of the advantages offered by the present invention.
A common method of serializing axial lead components from a bulk stock is to employ a vibrating bowl. Bulk components are fed into the bowl, and vibrations of the bowl, in conjunction with the force of gravity, cause components to align with an exit of the bowl. Parts leaving the bowl enter a vertically disposed track. The longitudinal interior cross section of the track is just slightly larger than the body of the axial lead component, maintaining components within the track in a serialized, single file disposition. Longitudinal slots run the full length of two parallel sides of the track. The slots are wide enough to permit the component leads to protrude through the slot, yet small enough to prevent the body of the component from protruding through the slot.
The parts-carrying tracks often have a zig-zag, or sawtooth slot disposition, rather than being straight tracks. The zig-zag path slows the vertical descent rate of the part to a desired value less than what would be achieved by free-fall of the parts. Furthermore, parts queing which occurs at sawtooth vertices tends to bring parts within the track into an adjacent, parallel configuration, with bodies of the parts essentially horizontal.
Parts that have once entered the zig-zag track from a vibratory bowl feeder usually travel without difficulty. However, vibratory bowl feeders are frequently plagued by jams occurring within the bowl and at the bowl exit. Also, the susceptibility to jamming of vibratory bowl feeders is aggravated by even slight bends in the component leads.
To handle components with magnetic leads, feeders using magnetic fields have been frequently employed. One obvious disadvantage of magnetic-field feeders is the limitation of their usage to components having magnetic leads. Also, most magnetic component handlers employ a flux field that holds components in stable equilibrium independent of component polarity. The polarity-insensitivity occasionally permits a part to flip over to an incorrect orientation.
Other axial lead component handling machines have employed air jets or vacuum, or a combination of the two, or contacting mechanical actuators to force the components into wheels or slots prior to testing or routing the components to subsequent manufacturing stations. These machines generally require that the components be first brought into parallel alignment and serialized, using a vibratory bowl feeder for example. An additional disadvantage of the present class of machines is their susceptibility of jamming, aggravated by out-of-tolerance components or components with bent leads.
Several drawbacks are common to all previously-disclosed axial-lead components handling machines. These include: Complexiy, cost, jam-susceptibility, difficulty of maintaining and limited parts-handling rate capabilities.
The present invention overcomes the above-described shortcomings of previous methods of handling cylindrical components. It possesses novel features that afford superior performance of the tasks of serializing bulk components for single-file distribution, testing the components, orienting components to either of two positions opposed 180 degrees from one another, rejecting out-of-tolerance components, and delivering oriented parts to a destination selected from a plurality of available destinations.
The present invention is well-adapted to function at high through-put rates of tens of thousands of parts per hour. The three major subsystems of the machine, namely, the feeder-serializer, the test station, and the orienter are each capable of functioning as independent units. Thus, all or some of the subassemblies may be used in various combinations to suit the particular user's parts feeding and serializing, testing and orienting requirements.
Several novel features of the invention together provide the high parts-handling rate capability.
For example, the test head, as is described in more detail below, employs linearly actuated inclined planes to grasp a component to be tested, force the component into the test position, and force the tested component out of the test position upon completion of the test. This test head actuation method overcomes the speed limitations inherent in testing methods relying primarily on gravity to move components under test.
Also contributing to the high speed capability of the present invention is the fact that components are tested while remaining in the feeder track which routes the components to and from the test station. This eliminates time-consuming transfer operations to and from the test station, as are required with previously existing methods.
The present invention is well adapted to high-speed handling of small cylindrical parts in addition to axial lead electronic components, as will be apparent from the following descriptions.